Railway signaling system



y 1934- J. c. HOFFMAN 1,967,555

RAILWAY S IGNALING SYSTEM Filed Sept. 6, 1952 s Sheets-Sheet 1 *f Q IL i1 v 7 MM 3 3 W JAY c- Harp/w "F in, 554;; W

y 1934. J. c. HOFFMAN 1,967,555

BAILWAY S IGNALING SYSTEM [1 Filed Sept. 6, 1952 5 Sheets-Sheet 2 Flag July 24, 1934- J. 'c. HOFFMAN RAILWAY SIGNALING SYSTEM k Fi led Sept. 6. 1952 5 Sheets-Sheet 3 Patented July 24, 1 934 UNITED STATES PATENT OFFI'CE 4 Claims.

My invention relates to railway signaling systems such as automatic electric block-signal systems, using direct current and a normally closed track circuit. In these systems in which the shunting of the track circuit by rolling stock 1 required at this time to operate the track circuit than in dry weather. The amount of current required to properly operate the track circuit during wet Weather periods is of course substantially in excess of the amount of current required to properly operate the track circuit during dry weather periods. Accordingly, the current flow in the track circuit must be regulated, otherwise under certain conditions the track relays, controlling the circuits for the block signals,

. become less sensitive in response to a train shunt,

or a broken rail within the track circuit than while under other conditions, and consequently there is danger of the relays remaining energized and producing a false signal indication.

At present such conditions in a track circuit are partly controlled by an adjustable resistance unit connected in series with the battery of the circuit and so adjusted that the current flowing in said circuit is suflicient to actuate the track relay, when maximum current losses are experienced. To reduce the losses it is customary to subdivide the track circuit between two block signals into two circuit sections and to have in-- spectors and repairmen adjust the adjustable resistance unit prior to wet and dry Weather seasons, so that the signal system may function more effectively during such seasons.

However as manual supervision and regulation has its objections and limitations it has been proposed to provide automatic means for regulating the current flow in the track circuit which means automatically cut in a resistance unit, arranged in series with the normally closed track circuit, when the current flow in said track circuit reaches a predetermined energy, thereby maintaining the sensitiveness of the circuit to a train shunt or a broken rail.

The means used in such automatically regulated track circuits are the ordinary tractive armature direct current relays, the operating char-- acteristics of which are such thatsubstantial difierences in energies are required to attract the relay armatures and to hold the armatures in attracted position. As these energies differ to the extent of sixty percent and even more it can be seen that ineffectivenessof the automatically actuated energy adjusting means spreads over a substantial area of the changes of the resistance of the track circuit.

The general object of my present invention is to regulate the current flowing in a track circuit more readily and accurately than heretofore, by providing more sensitive automatic regulating means. For such purpose I use a special tractive armature direct current relay embodying a common electro-magnet with two coiis and an armature. This relay is shunted to the normal track circuit and actuates a subdivided resistance element, the subdivisions of which are adapted to be connected in parallel with the shunt circuit of the normal track circuit when the armature of the relay is released and to be connected in series with the normal track circuit when said armature is attracted. The resistance element is dimensioned to reduce the flow of current in the track circuit and to increase the flow in the shunt circuit, when said element is connected in series to the track circuit, because the actual resistance of the shunt circuit decreases when the subdivisions of said resistance are cut out of the shunt circuit. The force of the electro-magnet is adjusted to hold the armature attracted, when the resistance is cut out of the shunt circuit bya slight increase of the current in the track circuit, and the following decrease of the current in the shunt circuit effects release of the armature. Such release of the armature causes the resistance element to be disconnected from the'track circuit and therefore increases the current flowing through the track circuit, but also causes the subdivisions of the resistance element to be connected parallel to the shunt circuit. The increased flow of current in the track circuit affects merely a nominal change of flow of current in the shunt circuit, so that the armature of the relay is picked up or released within very close-energy ranges when compared with the ordinary relays.

Still better results, according to my invention will be accomplished by the use of special tractive armature direct current relays provided with a gravity actuated pawl coupled with and actuated by the tractive armature by means of a lever member attached to and actuated by the armature.- This lever member closes a spring contact when the armature is released. I The gravity actuated pawl interlocks with a latch dogon the spring contact and thus secures the spring contact in cicsed position, but upward movement of the armature to its fully attracted or pick up position causes disengagement of said pawl and therewith opening of the spring contact.

The special relay embodying the gravity actuated pawl and latch mechanism and the spring contact referred to above permits the connection anddisconnection of aresistance in series' with lever J lifts pawl H sufficiently so that said pawl the normal track circuit and relays, and thus the decrease and increase of the magnetic forceof the relays in such degree that their armatures are picked up and released within narrow ranges of current flowing through the coils of the relays.

The current flow of the track circuit is preferably controlled by two of the self regulating relays referred to above, which are so coupled with each other and the circuit, that 'one of said relays controls and regulates the current fiow in the track circuit, when the track is unoccupied and the other one of said relays is actuated when the track is short circuited by a train or car.

In the accompanying drawings: Figures 1, 2 and 3 are diagrams of a section or block of a railway signaling system having selfregulating relays in circuit therewith, and showing the operation thereof under different conditions.

In these drawings the relays A and B are in some respects similar to the direct current tractive armature relays ordinarily used in connection with track circuits, in that each embodies a pair of magnet windings or coils 2 and 3, and the an armature K hinged opposite the'pole pieces E. Armature K carries a contact member N to make and break the shunt line at 6 for a purpose later to be described. A spring lever J is rigidly secured to armature K and actuates a spring contact lever L. Thus when the armature K is in released or down position an angular extension 7 on lever J forcibly pushes the spring lever L into contact with contact member 4, thereby permitting tilting of pawl H andthe engagement of its notch R with a latch dog M on spring contact lever h to lock said lever in contact position with its contact member 4. When the armature K is picked up and almost drawn to its picked up or upward position an upwardly'extended arm 9 on disengages latch dog M and permits spring contact member L to break its contact with contact member 4.

The features which distinguish the relays from others known tome reside principally in the use of the pawl and latch mechanism described above and the method of connecting a resistance element F in series with the operating track circuit.

The relays used by me are preferably of the slow releasing type which are so adjusted that their .armatures will be picked. up or attracted when a predetermined rate of current flows through the magnet coils of said relays. In such relays the adjustment to proper pick up action f is made by changing the air gap between the mag- .and 3, as for example in a dry weather period in which losses through ballast and cross ties of the track circuit are low, then the magnetic force of coils 2 and 3 is suflicient to attract armature K, so that armature contact member N breaks the contact of the shunt line at 6. This contact break causes resistance element or unit F to be cut into the track circuit so that the rate of current flow in this circuit will be substantially decreased. A substantial decrease of the rate of current flow in the said track circuit in, turn common pole pieces E. Each relay also'includes' automatically increases the flow of current in coils 2 and 3, though the actual resistance of the circuit including these coils is increaseddue to the fact that the right portion of resistance F has been cut out. This right hand portion of resistance unit F had been connected in parallel with the left portion of resistance F, and therefore decreased the actual resistance of said left hand portion with respect to the circuit. The increased rate of current flow through magnet coils 2 and 3 permits the completion of the pick-up operation of armature K, whereupon contact member N makes contact with contact 5; Finally spring lever J lifts pawl H and causes latch dog M to disengage so that spring contact member L can breakits contact with contactmember' l. In the action just described the predetermined resistance value of the resistance unit F and the change of potential at center'tap l0of said unit causes a definite reduction of the current flow in magnet coils 2 and 3 and therewith the magnetic force of the relay, so that a slight decrease in the potential. of the track circuit is sufficient to cause release of armature K of relay A. The sensibility ential windings, viz, low resistance windingsQ and high resistance windings 2 and 3'. Themagnet coils 2- and 3 of relay A are of the single winding type. r The closed track circuit T, which ordinarily extends over one half of the length of a block, the space between two adjoining block signals, is insulated from adjoining track sectionsby insulated rail joints P, P. In circuit T the relaysA and B, the adjustable resistance elements E, F and F, local connecting circuits and battery'D are arranged at one end, whereas a track relay C of ordinary type is arranged at the opposite end of said track circuit adjacent to a signal S. v

The resistance E is so adjusted that when the track circuit is not short circuited the magnetic field of low resistance windings Q is insufficient to pick up armature K of relay B and'that when greatest losses through cross ties and ballast occur the current flowing through the track circuit and the auxiliary energizing circuits is insufiicient to cause picking up of armature K, of relay A so that both ar matures stay dropped, but such current must be sunicient to actuate trackrelay C. Under these conditions the current flows from battery D through adjustable resistance E, thence to the low resistance'windings Q'of relay B, its armature'contact member N and contact 6 and'thence to contact 6 of relay A, its armature contact member N, to and through rail 8 and the magnet winding coils of relay C and returning. over rail 8' to battery D. A negligible amount of current is shunted through an auxiliary energizingcircuit of relay A, beginning at'center tap 10 of resistance over contact 4 and contact spring L to and through coils 2 and 3 to point 11. A decrease of the current losses through cross ties and ballast decreases the flow of current in the track circuit and when such losses have been substantially reduced, as in a dry Weather period, the current flow in the closed track circuit will resemble the diagram represented in Figure 2, which diagram shows that the current energy in the track circuit has been automatically regulated by change of the path of the current in the closed track circuit. Thus the current in the track circuit flows from battery D through resistance E to and through the low resistance coils Q of relay B, thence through contact member N and contact 6 to and through resistance F to rail 8, coils of relay C, returning over rail 8' to battery D, whereas the current of the auxiliary energizing circuit beginning at center tap it of resistance F has been cut off, because this circuit is now interrupted at contact member 4. This change of the path of the current of the track circuit and the cutting out of the auxiliary energizing circuit referred to above is caused by the increase of the current flowing through the circuits delineated in the diagram of Figure 1. Thus the increase of current in the auxiliary energizing circuit causes armature K to be picked up and to slightly open contact member N at contact 6, whereby resistance F is switched into the track circuit. This reduces the current flow in the track circuit and causes a further increase of the current flowing through coils 2 and 3 of relay A, because thepotential at center tap 10 of resistance F is substantially increased. Consequently, armature K is completely picked up and contact member N contacts with contact 5 in advance of the opening of the contact between spring contact L and contact member 4. Opening of the contact between spring contact L and contact 4 is caused by member J which by means of its arm 9 tilts the pawl H so that said pawl is disengaged from latch dog M and coil windings 2 and 3 are connected to the circuit together with the track side of resistance F which resistance insures that the armature K of relay A will be released and thereafter cause resistance F to be cut out in the event of a slight decrease in e resistance of the track circuit.

Short circuiting of the track circuit by a wheeled truck or car causes the current flow in the track circuit to follow the diagram shown in Figure 3, which shows that the wheels and axles of the truck short-circuit that part of the track circuit which includes relay C, so that said relay releases its armature U, in turn actuating a signaling circuit P for signal S. The release of armature U of relay C is followed by the release of the armature K of relay A, which is slower in releasing action than relay C, to prevent the cutting out of resistance F before the armature of the common track relay C has been released and to insure proper action of the signaling circuit P under all possible conditions.

A short circuiting of the track relays increases the flow of current in the shunted track circuit considerably in excess of the current flowing through said circuit during wet weather periods and therefore the resistance F at relay A is shunted out of the track circuit. Under these conditions the current flows from battery D to and through resistance E, low resistance Windings Q of relay B, thence to and through resistance F and F over rail 8, the truck Wheel and rail 8 back to battery D, because the current flowing now through low winding coils Q is sufficient to cause the armature K of relay B to be picked up and thus open the contact member 6. Current also flows through an auxiliary energizing circuit from the center top 10' of resistance F through coils 2' and 3 to contact 4 and contact member L and thence to contact member 6 and contact member N to rail 8, through the truck wheels to rail 8 and back to battery D. This latter current causes the completion of the pick up operation of armature K and therewith lifting of pawl H by lever member J which action disengages said pawl from latch dog M and permits contact L to break its contact with contact member 4'. The breaking of the contact between contact member L and contact 4' cuts off the current flow in windings 2 and 3, whereas a reduced amount of current continues to flow through low winding coils Q. This reduced amount of current is predetermined by the setting of adjustable resistance element F and must be slightly higher than the current ratio at which relay B releases its armature K, when the short circuit is broken by moving the rolling stock out of the track circuit section.

Having thus described my invention what I claim is:

1. In a tractive armature relay adapted to automatically control the flow of current in the track circuit of a railway signaling system, a main circuit, an auxiliary circuit shunted with respect to said main circuit, switching means for said circuits, electromagnetically actuated controlling means for said switching means having their electromagnets connected in series to said auxiliary circuit, and subdivided resistance means connected in parallel to said main circuit, the sections of said resistance means being connected parallel to each other and jointly connected in series to said auxiliary circuit, and said switching means being adapted to connect said resistance means in series with said main circuit and disconnect the sections of said resistance means from said auxiliary circuit.

2. In a tractive armature relay according to claim 1, switching means including a main switch adapted to switch oi? one of the sections of said resistance means from said auxiliary circuit and a spring contact member adapted to switch oil the other section or said resistance means from said auxiliary circuit, said spring contact mem- 7 her being provided with automatic locking means for retarding the opening of said contact member and said locking means being controlled by said electromagnetically actuated controlling means.

3. A tractive armature relay device adapted to automatically control the flow of current in the track circuit of a railway signaling system comprising a main circuit, two tractive armature relays connected in series with said main circuit, each including a single armature and magnet coils, an auxiliary circuit for each or" said relays connected in parallel to said main circuit and controlled by the armature of the corresponding relay, and subdivided resistance means for each of said auxiliary circuits connected in parallel to said main circuit, the sections of said resist .ance means being connected parallel to each other and jointly in series to said auxiliary circuit, and said switching means being adapted to connect said resistance means in series with said main circuit and disconnect consecutively the sections of said resistance means from said auxiliary circuit.

4. A tractive armature relay according to claim 3 wherein one of said tractive armature relays includes a low resistance coil connected in series JAY C. HOFFMAN. 

